The present invention relates to a motor-driven compressor.
A motor-driven compressor includes a metal housing accommodating a compression unit, which compresses and discharges refrigerant, and an electric motor, which drives the compression unit. A cover that defines an accommodating chamber is coupled to the housing. The accommodating chamber accommodates a motor driving circuit that drives the electric motor.
When the cover is made of metal, the overall weight of the motor-driven compressor increases. The use of a resin cover allows for the motor-driven compressor to be lighter. However, a resin cover would transmit electromagnetic noise from outside the compressor to the motor driving circuit. In addition, electromagnetic noise from the motor driving circuit may leak out of the compressor through the resin cover.
Accordingly, Japanese Laid-Open Patent Publication No. 2008-215236 discloses a laminated cover including a conductive layer (shield), which is made of a conductive material such as aluminum and iron, and an insulating layer (resin portion), which is made of an insulating material such as resin and rubber. The cover is coupled to a housing by a bolt, with the conductive layer in contact with the housing. Electromagnetic noise from the exterior is blocked by the conductive layer and transmitted to the housing. This suppresses electromagnetic noise entering the accommodating chamber through the insulating layer. In addition, electromagnetic noise from the motor driving circuit is blocked by the conductive layer and transmitted to the housing. This suppresses the leakage of electromagnetic noise from the motor driving circuit to the exterior through the insulating layer.
However, when the cover of the publication is coupled to the housing, the conductive layer and the insulating layer are held between the housing and the bolt. Thus, the axial force of the bolt tends to deform the insulating layer. Deformation of the insulating layer may loosen the bolt and adversely affect the seal between the housing and the cover. This may result in foreign matter or water entering the accommodating chamber through a gap between the housing and the cover.